A sliding bearing for automobile engine is normally made of aluminum alloy or copper-lead alloy with Pb-based overlay. In the art of this kind of a sliding bearing, it has heretofore been practiced to enhance the abrasion resistance, seizure resistance and initial conformability of the sliding bearing by coating the surface of the bearing alloy layer with a coating layer comprising a solid lubricant incorporated in a resin such as polyamide-imide, polyimide and epoxy resin.
For example, Patent Reference 1 (JP-A-4-83914) discloses that the use of a sliding bearing material having a coating layer made of from 55 to 90% by weight of a solid lubricant and from 10 to 45% by weight of a polyimide-based binder formed on the surface of an aluminum bearing alloy makes it possible to enhance the initial conformability of the aluminum alloy bearing and have excellent fatigue resistance and seizure resistance.
Further, Patent Reference 2 (JP-A-7-247493) discloses that the addition of a film forming aid to a solid lubricant film made of from 70 to 97% by weight of a solid lubricant and from 3 to 30% by weight of a resin selected from polyimide resin, epoxy resin and phenolic resin makes it possible to provide firm retention of solid lubricant and good conformability that give excellent seizure resistance which prevents exfoliation and hence enhances abrasion resistance.
On the other hand, Patent Reference 3 (JP-A-2002-61652) discloses a sliding bearing comprising a resin coating layer formed on a bearing alloy layer, which resin coating layer comprises a soft high-temperature extensible thermosetting resin having a tensile strength of from 70 to 110 MPa and an elongation of from 7 to 20% at 25° C. and a tensile strength of 15 MPA or more and an elongation of 20% or more at 200° C. and a solid lubricant in an amount of from 70 to 30 vol-% and from 30 to 70 vol-%, respectively, and has a Vickers hardness Hv of 20 or less. This sliding bearing is excellent in initial conformability and seizure resistance as compared with those of Patent References 1 and 2 but leaves something to be desired in physical properties required for automobile high speed engines.
In recent years, the performance of automobile engines have been remarkably enhanced for higher output and higher rotary speed, and the appearance of sliding bearings excellent in sliding properties, particularly initial conformability and seizure resistance, as well as in durability and heat resistance has been desired.    [Patent Reference 1] JP-A-4-83914    [Patent Reference 2] JP-A-7-247493    [Patent Reference 3] JP-A-2002-61652